Making Waves and Pulses
With the Brain's Neurons
Neurons cluster in minicolumns.  Shown here are 3 of the
approximately 100 neurons in one of the 3 hundred million minicolumns
that make up the human cerebral cortex.
Close-up view of a single neuron,
with its long vertical fiber (apical dendrite), its bush-like
group of short fibers (basal dendrites), and its thread-like fiber
(axon). Many of these apical dendrites have lengths that are 600
times their diameters (imagine a plastic tube, 6 inches in diameter, the
length of a football field). A series of signals arriving near one
end would not be faithfully transmitted to the other end.
Animation of pulses being processed
through the neuron. (Animation may be temporarily slow while loading)
  Pulses that arrive at a basal dendrite fiber
produce a surge of electric current that travels the short distance to
the pyramid-shaped cell body, which converts the electric current
into another pulse that travels along the axon fiber to another
neuron. Typically many pulses arrive simultaneously on several
dendrite fibers, and sum their currents at the cell body, and the cell
body then sends out a train  of pulses along the axon fiber to
other neurons.
Animation of the wave.
(Animation may be temporarily slow while loading)
  A series of pulses arrives at the long apical dendrite in a regular,
repeating rhythm, and produces surge after surge of current. These
rhythmic surges of current make up a wave. When waves are synchronized
in thousands of long apical dendrites which are clustered closely
together and aligned in the same direction, the intensity of the
combined wave produces an electric field that spreads to the surface
of the brain and can be measured on the scalp as the well-known
electroencephalogram(EEG). Electric current surges in the long apical
dendrites may not reach the cell body to produce output pulses in the
axon in the way current surges in the basal dendrites do. However, waves in
the apical dendrite may influence the input-throughput-output
processing of pulses that takes place via the short basal
dendrites. The rhythmic surges of current that make up the wave on the
long apical dendrite are believed to produce the subjective experiences of
sustained attention and consciousness.
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Updates |
  31 Jan 01 -Wave animations posted to the site.
  18 Oct 02 -Pulse animations added to the site. |
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